Recovery of tar acids



Jan. 16, 1934. s. P. MILLER RECOVERY OF TAR ACIDS Filed April 19, 1950INVENTO 5. 7 7 -W- ATTORNEYS Patented Jam 16, 1934 1,944,131 RECOVERY orran ACIDS Stuart Par-melee Miller; Englew ,IN. 1., p

signor to The Barrett Company, New Yprk, N. Y., a corporation of NewJersey Application April 19,1930. Serial No. 445,617

9 Claims. (01'. 202-67) This invention relates to improvements in therecovery of tar acids as a by-product oi? the operation of coalcarbonization plants such as coke oven batteries or gas retort plants orlow tem-' 5 perature carbonization plants with the simultaneousproduction of a bituminous residue which may be a low melting pointpitch. It includes the bituminous residue or pitch as a new product; Thetar acids may be recovered as such, or as a tar acid oil.

- The invention will be particularly described with respect to cokeovens of the lay-product type.

In the ordinary operation of the common types of coke oven batteries,the coal distillation gases from the individual ovens are collected in agas collector main where they are partially cooled, and from there theypass to condensers where they are further cooled. A heavy tar is sepa-.20 rated from the gases by the partial cooling of the gases in thecollector mainand such scrubbing'of the gases as is incident to thecollector main operation. A' light tar or tarry oil is separated fromthe resulting gases in the condensers. The heavy tar and light tar ortarry oil fractions are ordinarily blended together and .the resultingtotal tar is distilled or burned as fuel or is otherwise disposed of.

According to this invention, the various tar so fractions recovered fromthe -coke oven gases are not blended but at least one fraction isseparately recovered and treated for the removal of tar acids and theproduction of a low melting point pitch. According to a preferred methodof carrying out the invention, two separate tar fractions are recoveredfrom the coke oven gases, namely a heavy tar from the collector main anda tarry oil from the condensers. .Thetarry oil is then treated for itstar acid content and a bituminous residue is produced, which may be alow melting point pitch or a thinner, more fluid material.

Coke oven gases vary in composition, depending upon the kind of coaltreated and the temperature of the distillation. The tar produced variesaccordingly and moreover the tar fractions vary, depending upon theextent to which the gases are cooled in the collector main, etc.

The most widely used commercial types of tar 5 0 acids have boilingpoints within the range between about 100 and'230 C. The tar whichseparates in the. collector main of a coke oven battery contains asmaller percentage of tar acids than the tarry oil from the condensers.

According to a preferred method of carrying were distilled.

out this invention, the cooling in the collector main is regulated topermit as large a portion as possible of the tar acids to pass over intothe condensers and thus produce a tarry oil of relatively high tar acidcontent, as compared with the total tar or with. the heavier tar fromthe collector main.

As one example of tar acid distribution in such tar fractions it wasfound that the tarry oil from the condensers of an ordinary coke' ovenbattery contained a large percentage (about fifty or more percent) ofoils boiling within a narrow temperature range, (between 210 and 220 C.vapor temperature) and that the oils of this I boiling range were highin tar acids. 0n the other hand, neither the heavier tar separating inthe collector main nor the total tar produced if all tariractions werecollected together as is the usual practice contained such largepercentages of narrow boiling range oils; the boiling point of oils fromsuch tars (to, say, Ditch of 105 F. melting point) rose quite rapidlyduring the early portions of a test distillation and again after thirtyor forty percent of oils The amount of oils boiling near the tar acidrange contained in total tar, or intarry oils separated and treated asin this process, will vary with the composition and conditions ofproduction of the tar. The tar acid oil fraction accompanying the taracids, when these are recovered by distillation, may therefore varyconsiderably from the example given. In all cases, however,,tarry oilsmay be recovered and worked up as described which have a higher tar acidcontent than the total tars of which they are respectively fractions.The distillation of the tarry oils from the condensers is preferably socontrolled that although the lower boiling tar acids are volatilized,the major portion of the less ,95 valuable higher boiling acids is leftin the pitch residue. v

- Tar acids can he recovered from the tarry oils from the condensersmore efliciently than from total tar or from the heavy tar from the col-1 lector main because of the relatively greater percentage of tar acidscontained in the tarry oils. The residue which remains aftervolatilization of the tar acids is a low melting pitch suitable forindustrial use, e.g. for fuel. The tar acid oils may be distilled fromthe tarry oils in any suitable type of still. The distillate may beextracted with caustic or other alkaline reagent to recover the taracids and the resulting neutral oil. The neutral oils may be blendedwith the coal distillation gases from selected ovens o1 ,the' plant, inthe form of a fine intense spray,

as more fully described in application Serial No. 326,771, filedDecember 18, 1928 or application Serial No. 326,769, filed December 18,1928 The tarry oils may be distilled in steam or other hot gases or inan ordinary tar still or by any other suitable means. Preferably the taracids are volatilized from the tar without substantial decomposition ofany of the constituents of the tar, and it the neutral oils remainingafter extraction oi tar acids from the distillate are retprned to thedistillation residue, the resulting product is of substantially the samecomposition as the original tarry oils except for the absence of the taracids. It is a dephenolized or partially dephenolized tarry oil.

In the accompanying drawing, three curves A, Band C are shown by way ofexample, which are test distillation curves of distillate oils from tarsfrom a Semet-Solvay coke oven battery and are representative in ageneralv way of distillates from the total tar, heavy tar and tarry oil,respectively. It is to be noted that the distillate from the tarry oilfrom the condensers after being heated to a temperature of 205 or 210C., shows little additional rise in temperature until about 75% 01' theoil has been distilled off. Neither the distillate from the total tar,i. e. the blend of the tarry oil and heavy tar, nor from the heavy tar,shows on distillation any such gradual rise in temperature over aprolonged period of time. A large percentage of the oil may be distilledfrom this tarry oil without producing a high melting point pitch. Thedistillation oi the tarry oil can be controlled so as to produce adistillate of high tar acid content and yet yield a pitch of low meltingpoint, for example, a pitch with a melting point between 100 and 110 F.

The tar acids may readily be extracted from the distillate and theremaining neutral oils may be blended with creosote oil.or be otherwisedisposed 01. According to one method oi"carrying out the invention,these neutral oils are blended with the distillation residue to producea product suitable for fuel. This is particularly advantageous at plantsproducing large amounts of tar and having a large demand for liquidfuel, e. g. coke plants connected with steel plants.

The distribution of the tar acids in the tar obtained from coke ovengases'is indicated in a general way in the following example, althoughit is to be understood that the percent oi.

tar acids present in the tar and the composition of the tar vary withthe kind of coal coked and the temperature of coking, etc. In generalthe higher the coking temperature the lower the tar acid content,although the'tar acid content depends to large extent upon the kind ofcoalbeing ocked, the speed of coking, the design 01 the distillationresidue to form a product suitable sent 3% of the total tar, the tarryoil will have a tar acid content of about 4.3% and the heavy tar willhave a tar acid content of only about 2.3%. If the tarry oil isdistilled to pitch with a melting point of about 105 F., and ofdistillate is obtained, this will ordinarily contain about of the acidspresent in the tarry oil. This distillate will constitute about 12.25%by volume of the total tar and will contain about 1.125 parts by volumeof tar acid per parts of the total tar recovered. It will have a taracid content of about 9.2%. The distillate from the tarry oil would havethe following analysis: 7

10% crude coal tar light oils 9% tar acids i 61% crude naphthalene 20%creosote oil The tar acids can be recovered from this distillate in anysuitable manner as by extraction with caustic soda to produce carbolateand the acids can then be regenerated from the carbolate byacidification with carbon dioxide, suliuric or other acids. 100

As another example may be taken a tar produced from a Koppers battery.The total tar had a tar. acid content of 2.3%. By separately collectingthe heavy tar deposited in the collector main and the tarry oilscondensed in the condensers, however, the latter were obtained with atar acid content of 5.4%. By distilling this tarry oil fraction, (say,18-25% of the total tar) it was possible to obtain an oil rich in taracids and well suited to the usual 11 tar acidv extraction with causticsoda. It was thus possible toobtain a substantial yield oi tar acidseconomically by this method with the distillation of only a relativelysmall portion of the tar, (e. g. to V irom tars of low tar acid content,from which the recovery of tar acids by the usual process would often beuneconomical.

While theadvantages of the method are not restricted to tars of low taracid content in the total tar, they are especially marked when the totaltar has a content of 3% or less of tar .acids'.

- The pitch remaining after tar acid oils have been volatilized from thetarry oils with or 2 without the neutral oils of the same boiling rangeas the tar acids, may be blended with the heavy tar from the collectormain or with tarry oil from the condensers or other tar for use as fuel,although stripped tar or the dephenolized tar remaining after theremoval of tar acids from the tarry oils is suitable for use as fueldirectly.

In general, the method of this invention permits recovery of a givenamount of tar acids from a given tar with distillation or treatment ormuch less tar than the usual method, and (it the oil is extracted withcaustic soda) with the extraction of much less oil.

Furthermore, the tar acids so recovered, or contained in the oils sorecovered, are of a lower and more desirable boiling range than thanrecovered from a corresponding total tar by I the usual methods.

I claim; l. The improved method of recovering coal tar acids, whichcomprises iractionally cooling the coal distillation gases from a coalcarbonization plant so as to recover a heavy tar rela: tively low incoal tar acids and a tar oil of relatively high coal tar acid content,and sepa-' rately recovering the coal tar acidsfrom the tar Ollj 2. Theimproved method of recovering coal tar acids, which comprises coolingthecoal dis-.-

tistillation gases from a coal carhonization plant so as to recover aheavy tar relatively low in coal tar acids and a tarry oil of relativelyhigh a coal tar acid content, and separately treating the tarry oil torecover the coal tar acids therefrom and produce a bituminous residuelow content and a low melting point coal-tar pitch suitable for fuel.

4. The improved method of recovering coal tar acids, which comprisespartially cooling coal distillation gases in the collector main of acoke oven battery and separating heavy tar from the gases therein,further cooling the gases in con-' densers to produce a tarry oil,separately collecting the tarry oil, separately distilling it to producedistillate of high coal tar acid content and a low melting pointcoal-tar pitch suitable for fuel, and extracting coal tar acids from thedistillate. v

5. The improved method of recovering coal tar acid oils, which comprisesfractionally condensing the coal distillation gases from a coalcarbonization plant to produce a tarry oil which on distillationyields'at least of distillate between 210 and 220 C., and distilling thetarry oil to produce separately distillate of high coal' l sten! No.1,944,131.

tar acid content and low meltingpoint coal-tar pitch suitable for fuel.

6. The improved method of producing a low melting point coal-tar pitchsuitable for fuel at a coal earbonization plant, which comprisespartially cooling -the coal distillation gases in the gas collector mainso as to separate a heavy tar, further cooling the gases in thecondensers toproduce a tarry oil andseparately distilling the tarry oilto produce a coal-tar pitch with a melting point in the neighborhood of105 F. tar acids, which comprises partially cooling coal tar acids,which-comprises partially coolng coal distillation gases in thecollector main of a coke oven battery to. separate a heavy tartherefrom, further cooling the gases in the condensers to produce atarry oil and. separately distilling the tarry oil to volatilize coaltar acids and leave a distillation residue, extracting coal tar acidsfrom the distillate so as to produce a neutral oil and blending theneutral oil with the distillation' residueto produce a fuel pitch.

8. The method of treating coal distillation gases, the total tar fromwhich has a tar .acid content less than 3%, which comprises fractionallycooling the gases so as to produce a heavy tar fraction and a tarry oilfraction with a coal tar acid content greater than 3%, separatelydistilling the tarry oil fraction and extracting the coal tar acids fromthe distillate.

9. The improved method of recovering coal tar acids from the coaldistillation gases of a coal distillation plant which comprisespartially cooling the gases so as to recover a heavy tar comprisingabout of the total tar ,constitu- 110 ents of the gases, further coolingthe gases to condense a tarry oil comprising about 35% of the total tarconstituents orginally present in the gases, and separately treating thetarry oil it is hereby certiiiedthat error appears in the printedspecification of the. above numbered patent requiring correction asfollows: Page 3, line40, claim 5, strike out the word "separately" andinsert the same before "distilling" inline '39; same page, strike outline 87, comprising the words "tar acids, which comprises partiallycooling coal" andinsert instead as the first line.

of claim 7, 7. The improved method of recovering coal;

Letters Patent should be read with these corrections therein that thesame may conform to the record of the case in the Patent Office. .Signedand sealed this 6th day of March, A. D. 1934.

(Seal) to recover coal tar acids therefrom.

s. P. MILLER.

CERTIFICATE or CORRECTION. Q

i January 16, 1934.

STUART PARMELEE' MILLER.

and. that the said F. M. ,Hopkins Acting Commissioner of Patents.

